Sounds like something is dragging

It sounds like something is intermittently dragging behind my car - like a light piece of metal dragging on the ground. I pulled over twice to look, and everything appears ok. There is also a weird noise that sounds like it could be coming from the trunk - a low pitch rattle. I drive a 2002 Ford Focus manual and this just started today while driving straight on residential streets. Any ideas?

If your car has drum brakes, it could be something inside the rear brakes making that metalic noise on the brake drum.
If you can see nothing with the car up on a hoist, then inspect the rear brakes by removing drums.

Get it up on a lift and start by checking the brakes and the exhaust system.